Airfoil including fluidically controlled jet flap

ABSTRACT

Controlled deflection of a jet flap emanating from an airfoil is accomplished by control fluid streams aligned at a substantial angle to the fluid jet which produces the jet flap. Disclosed embodiments show the use of the fluidically controlled jet flap to adjust the attitude and/or airfoil loading of an aircraft, to generate oscillatory lift forces for flight flutter testing of an aircraft, and to generate and control gusts in wind tunnels.

D United States Patent 51 3,669,386 Jaco et al- [451 June 13, 1972 [5AIRFOIL INCLUDING FLUIDICALLY [56] References Cited CONTROLLED JET FLAPUNITED STATES PATENTS t Willi axlmi [72] both 33x52 mm F 3,362,6601/1968 Tyler ..244/42 cc [73] Assignee: Lockheed Aircraft Corporation,Burbank, m y Examiner-Milton Buchler Calif. Assistant Examiner-Carl A.Rutledge ArtorneyRoger T. Frost and George C. Sullivan [22] Filed: May25, 1970 q 2| 1 Appl. No.1 40,270 [571 ABSTRACT Controlled deflection ofajet flap emanating from an airfoil is accomplished by control fluidstreams aligned at a substantial if 224/42 Cc angle to the fluid jetwhich produces the jet flap. Disclosed 1 '3" b l ,5 embodimentsshowtheuseofthe fluidicallycontrolled jet flap [58] Fleld of Search ..244/42CC, 52, 90, 40 to adjust the attitude and/or ail-f0 loading of anaircraft to generate oscillatory lift forces for flight flutter testingof an aircraft, and to generate and control gusts in wind tunnels.

8 Claims, 7 Drawing Figures PATENTEnJuu 13 m2 SHEET 1 OF 4 CONTROLVALVES ATTITUDE CONTROL SIGNAL 1N VEN TORS E U W S EL A V. JM Fm FM IM Al AIR PRESSURE SOURCE PAIENTEnaummz 3.669.366

SHEET 2 OF 4 VARIABLE SPEED INPUT AIR PRESSURE SOURCE INVENTORS WlLLl F.JACOBS MAXIMILIAN .P LATZER PATENTEDJUN 13 I972 3.669386 sum 3 or 4 FIG5 TUNNEL ROOF JET SHEET /7,f

TUNNEL FLOOR NN-MH .igliEET Am TEST MODEL FLOW INVENTORS WILLI F. JACOBSMAXIMILIAN F. PLATZER PATENTEDJUH13 I972 3. 669.386

sum u 0r 4 INVEN s WILLI F. JACO MAXIMiLlAN F. PLATZER Attorney AIRFGILINCLUDING FLUIDICALLY CONTROLLED JET FLAP This invention relates ingeneral to airfoils and in particular to airfoils including a jet flapthe deflection of which is fluidically controlled.

The problems involved in controlling the flight stability and theattitude of an aircraft have grown along with increases in the size andthe maximum speed of the aircraft. The flight control system of anaircraft must enable the aircraft to maintain stability in all plannedflight regimes, and this must be accomplished within the practicaldesign limits of control surface area, the amount and rate of deflectionof such control surfaces, and the structural load imposed on theairframe by the control surface deflection at operational speed.Aircraft designers, accordingly, have sought aircraft attitude andstability control techniques which produce the desired controleffectiveness and rapid response to manual or automatic inputs, whileminimizing negative factors such as added weight and complexity of thecontrolling apparatus, inability of the control surface to respond totransients such as gusts, and airframe fatigue.

Many techniques have been proposed in any attempt to overcome theforegoing problem. One of these techniques is known as the jet flap" andconsists of an arrangement of one or more fluid flow openings disposedalong the trailing edge of an airfoil such as a wing or a controlsurface. A gaseous fluid such as air is supplied to the fluid flowopenings through suitable ducting to establish a jet sheet which isblown substantially downstream of the airfoil trailing edge. This jetsheet operates in a manner known to those skilled in the art to cause aneffective increase in the apparent width or chord of the wing, or theportion thereof affected by the jet flap. Moreover, appropriate angularorientation of the jet sheet causes an upward or downward lifting forceto be applied to the wing so that the jet flap exhibits some of thefunctional characteristics of a control surface such as an aileron or arudder.

The vector direction of the liftmodifying effect which the jet flapimparts to an airfoil depends upon the angular alignment between theairfoil and the jet sheet emanating therefrom, as is recognized by thoseskilled in the art. For example, a jet flap mounted in the trailing edgeof a wing and producing a downwardly deflected jet sheet imparts to thewing an upward force component caused by the reduced static pressure onthe wing upper surface and the increased static pressure on the winglower surface arising from the effect of the jet flap on air circulationaround the wing, and imparts an additional upward force component causedby the reaction thrust of the air blown from the jet flap openings toestablish the downwardly directed jet sheet. Conversely, a downwardlydeflected jet sheet imparts negative or downward induced pressure liftand reaction thrust.

Prior art schemes have been proposed for selectively varying the angleof deflection of a jet flap. Such proposals have required the physicalmovement of some jet flap component such as a nozzle or a flowdeflecting structural member, a requirement which not only adds unwantedweight to the aircraft but which also requires additional actuatingapparatus in the relatively confined area of an aircraft wing or aportion thereof. Moreover, the use of mechanically actuated devices tocontrol the deflection of the jet flap poses control response problemsarising from the inertia of the mechanical deflection elements whichmust be manipulated and of the power actuators required for suchmanipulation. The frequency response limitations of a mechanicallyactuated jet flap deflection system have precluded the use of the jetflap in applications such as flight flutter testing or gust alleviation,for example, where the response time of the jet flap to a rapidlyfluctuating input signal must be minimized.

Airfoils including a jet flap having a variably deflectable jet sheetare also useful in nonflight applications such as wind tunnel airflowcontrol. for example.

Accordingly, it is an object of this invention to provide an improvedjet flap.

it is another object of this invention to provide an airfoil includingan improved deflectable jet flap.

it is still another object of the present invention to provide anairfoil having a jet flap which is selectively angularly deflectablewithout resort to mechanical fluid stream deflecting apparatus.

It is a further object of this invention to provide an improved flowcontrolling apparatus for use in wind tunnels or the like.

Other objects and many of the attendant advantages of the presentinvention will be readily apparent from consideration of the followingspecification relating to the annexed drawings in which:

FlG. 1 shows an aircraft equipped according to an embodiment of thepresent invention;

FIG. 2 is a section view taken along line 22 of FIG. 1;

FIG. 3 shows a schematic operating diagram of the apparatus depicted inFIGS. 1 and 2;

FIG. 4 shows an isometric and partially schematic view of anotherembodiment of the present invention as used to control the flow of airin a wind tunnel;

FIG. 5 shows a section operational view of the apparatus depicted inFIG. 4;

FIG. 6 shows still another embodiment of the present inven tion, asattached to an aircraft wing to induce testing forces therein; and

FIG. 7 shows a section isometric view of another embodiment of thepresent invention as built into an airfoil.

The present invention, stated in general terms, comprehends a jet flapcontained in an airfoil and including a main jet which is aligned toestablish a jet sheet extending generally as a continuation of theairfoil chord when the jet sheet is undeflected. One or more controljets are positioned to direct an airstream at a substantial angle to theundeflected jet sheet. The fluidic forces caused by impingement of thecontrol jet stream on the jet sheet cause the path of travel of the jetsheet to be deflected. The change in the direction of jet sheet flowcauses a corresponding change in the airfoil forces attributable to themain jet.

FIGS. 1, 2, and 3 show a particular embodiment of the present inventionapplied to an aircraft indicated generally at 10 and having wings I] and12. .let flap apparatus, as indicated at 13 and 14, is installed along agenerally outward portion of the trailing edges 15 and 16, respectively,of each of the wings. The jet sheet 17 produced by the jet flap 13 isdepicted by FIG. I as being deflected downwardly, while the jet sheet l8produced by the jet flap M is depicted as being deflected upwardly; theincremental forces imparted to the wings by the jet sheet deflectionsshown in FIG. 1, denoted by the arrows adjacent the wing tips, thus tendto impart a clockwise rolling motion to the aircraft, and so the jetflaps in the depicted mode of operation are functionally comparable toailerons. It will be understood of course, that the aircraft it] mayemploy conventional ailerons in addition to the depicted jet flaps.

The operation of the jet flap is more readily apparent from the sectionview of the view of the wing 11, as depicted in FIG. 2, and theschematic operational diagram of FIG. 3. A spanwise conduit or plenum 22is disposed in the wing 11 so that the plenum is adjacent the wingtrailing edge for at least the spanwise extent of the jet flap 13. Theplenum 22 is connected by suitable plumbing 23 and a valve 24 to asuitable fluid source, such as air pressure source 25. A number oforifices 26 communicate with the exterior of the plenum 22 and arealigned in a spanwise direction along the wing to direct pressurized airfrom the plenum in a direction generally aft of the wing trailing edge15 to form a jet sheet 17 which can be generally parallel with the wingchord when the jet sheet is undeflected. The air pressure source 25 canbe any suitable source. such as bleed air from one or more turbofanengines or fluid pressure derived from an auxiliary power unit containedon the aircraft.

Contained in the wing trailing edge in a spanwise direction are an uppercontrol plenum 27 and a lower control plenum 28, each of which ispositioned adjacent to the plenum 22 to be on opposite sides of andspaced apart from the region whereat air forming the jet sheet 17 exitsfrom the main plenum orifices 26. The upper control plenum 27 has aplurality of control orifices 29 positioned in a spanwise direction todirect a fluid stream from the upper control plenum downwardly andsubstantially perpendicular to the fluid stream emanating from the mainplenum orifices 26. The lower control plenum 28 similarly contains aplurality of control orifices 30 which are positioned in a spanwisedirection to direct a fluid stream from the lower control plenumupwardly and substantially perpendicular to the undeflected jet sheetproduced by fluid flow from the orifices 26.

The use of the orifices 26, 29, and 30 to direct fluid flow from themain plenum and the control plenum is for illustrative purposes only, itbeing understood that any fluid flow openings, such as slotscommunicating with the appropriate plenum and extending in a spanwisedirection along the wing, can be substituted for the aligned individualorifices.

The control plenums 27 and 28 are connected by respective conduits 34and 35 to control valves indicated schematically at 36, whichselectively supply air pressure from the source 25 to the controlplenums in response to attitude control signals received from 37. Theattitude control signals can be derived from prior art mechanisms suchas gyros, accelerometers, and the like, which produce an output signalin response to the position or the rate of movement of the aircraft.Alternatively, the attitude control signal can be partially orcompletely derived from pilot input to a control wheel. The attitudecontrol signals cause actuation of the control valves 36 to supply airpressure to the control plenums as appropriate to accomplish the desireddeflection of the jet sheet 17, outlined below. It is understood, ofcourse, that the other wing 12 of the aircraft has a similar arrangementof main plenum, control plenums, and control valves operative inresponse to the source of control signals 37.

In considering the operation of the embodiment described thus far,assume that the attitude control signal 37 has commanded the jet flapsto impart a right-hand or clockwise roll motion to the aircraft, asdepicted in FIG. 1. The control valve 36 open responsive to such signalso that air pressure flows from the source 25 through the conduit 34 tothe upper control plenum 27. If the jet flap is not already in operationat the beginning of the roll maneuver, the valve 24 also must be openedat the command of the pilot or another control signal to supply airpressure to the main plenum 22. At the same time, the roll controlsignal causes initiation of air flow into the lower control plenum (notshown) associated with the jet flap 14 on the wing 12. Referring now toFIG. 2, it can be seen that pressurized air supplied to the main plenum22 exists through the orifices 26 to form a jet sheet which is aimed ina substantially chordwise direction aft of the trailing edge of the wing11, if no pressurized air is supplied to either of the control plenums27 and 28. Since the upper control plenum 27 is pressurized, however,air flows from that plenum through the control orifices 29 to impinge onthe jet sheet 17 adjacent its point of exit from the orifices 26 andsubstantially at a right angle thereto. This impingement of thecontroljet on the main jet forming the jet sheet [7 causes the jet sheetto be deflected in a downwardly direction, as shown in FIGS. 1 and 2, itbeing understood that the jet sheet 18 extending from the wing 12 issimilarly deflected upwardly by pressurized air emanating from thecontrol orifices of the lower control plenum as sociated with that wing.This deflection of the jet sheets causes a corresponding change in theincremental force components resulting from the principles ofjet flapoperation, such as the jet reaction thrust and the jet-induced pressurelift of the jet flap, so that the incremental lift imparted to the wing11 by the jet flap is increased by the downward deflection of the jetsheet 17 while the incremental lifi imparted to the wing 12 by the jetflap is diminished or made negative, ie, a downwardlydirected force, bythe upward deflection of the jet sheet 18. The effect of this liftimbalance causes the aircraft to roll in a clockwise direction.

The attitude of the aircraft can be controlled by simultaneousdeflection of both jet flaps l3 and 14 in the same direction. Forexample, assume that the attitude control signal 37 includes a verticalaccelerometer connected to sense the rate of vertical movement of theaircraft. The accelerometer senses an unwanted upward accelerationresulting from the incremental lift generated by some transient factor.such as a sudden gust, and commands the control valves 36 to supplypressurized air to the lower control plenums of each of the jet flaps l3and 14 at a rate of flow selected to deflect the respective jet sheets17 and 18 to the extent necessary to reduce or overcome the unwantedincremental lift. The reduction or elimination of the unwanted lift issensed by the accelerometer to provide feedback for the attitude controlsystem. The wing load alleviation resulting from this attitude controltechnique extends the fatigue life of the airframe and also produces aless bumpy ride for the occupants of the aircrafi.

The present invention is especially useful in applications, asexemplified by the foregoing problem of gust alleviation, where a rapidresponse to an input signal is required. It can be seen that no movingparts are employed in the operation or deflection of the jet flaps.Movable valve elements contained in the control valves 36, being muchsmaller than the movable nozzle or deflector elements associated withprior art jet flap apparatus, are readily manipulated by electrical,hydraulic, or other techniques to provide the desired frequencyresponse. Alternatively, the control valve function can be accomplishedby fluidic switching techniques so that only the relatively small volumeof air required to switch a fluidic valve need actually be controlled bya movable component.

The fluidically controlled jet flaps of the present invention can alsofunction as spoilers, thereby avoiding the undesirable flow separatingand aerodynamic drag found in conventional spoiler systems.

Still another application of the present invention is found in theinducement of flutter forces to an aircraft undergoing flight fluttertesting. In lieu of the rotating vanes or eccentric weights employed inthe prior art to apply flutter-inducing oscillatory forces to the wingsof an aircraft, the jet flaps 13 and 14 can be operated in unison or asotherwise desired and at a relatively high rate of oscillation to applythe desired forces to the wing for testing purposes. For example,oscillatory forces of 30 cycles per second are readily applied toaircraft wings using the jet flaps of the present invention, with acontrol signal of the desired frequency being applied to the con trolvalves 36.

The present invention also can be used to impart flight flutter testingforces to an aircraft not normally provided with jet flaps. Theembodiment shown in H6. 6, for example, includes an airfoil 4] affixedin a spaced-apart relationship to the wing 44 of an aircraft by means ofpylons 42 and 43. A similar airfoil arrangement 47 is attached to acorresponding location on the wing 45 of the aircraft. Each of theairfoils 41 and 47 is equipped with fluidically deflectable jet flaps 46and 48, as described herein, with the necessary conduits supplyingpressurized air to the main plenums and the control plenums being routedthrough the pylons to the jet flaps 46 and 48. Pressurized air issupplied to the control plenums of either or both of the jet flaps 46and 48 so that the jet sheets emanating therefrom are deflected to applythe desired flight flutter testing forces to the wings. In a typicalapplication of the FIG. 6 embodiment the airfoils and supporting pylonswould be temporarily installed on an aircraft used for flight fluttertesting purposes, such installation requiring only the addition of thenecessary ducting to the respective jet flaps. The airfoils 41 and 47and the supporting pylons are readily removable if desired, once theflight flutter testing of the aircraft has been completed.

The apparatus depicted in FIG. 7 shows another embodiment of the presentinvention wherein the jet sheet is fluidically displaced to assumeeither of two discrete deflections. The airfoil 70 has a trailing edgemember 71 fixedly or movably retained by supports 72 or the like spacedapart from the remainder of the airfoil to define an upper passage 73and a lower passage 74. The passages 73 and 74 converge at a throatregion 75 which is connected by means of the passage 76 to the mainplenum 77. An upper control plenum 78 and a lower control plenum 79 areconnected by respective control fluid passages 80 and 81. The mainplenum 77 is connected to a suitable air pressure source and the controlplenum are selectively supplied with air pressure as described above inthe FIG. 3 embodiment.

Operation of the embodiment shown in FIG. 7 is accomplished by supplyingpressurized air to the main plenum 77 sufl'lcient to establish a jetsheet, and by supplying a relatively small flow of air to the one of thecontrol plenum 78 and 79 which causes the jet sheet to shift to thedesired one of the passages 73 and 74. For example, anupwardly-deflected jet sheet exiting from the upper passage 73 isobtained by pressurizing the lower control plenum 79 so that deflectioncontrol air enters the throat region 75 through the passage 81 to shiftthe jet sheet air flowing from the passage 76 to the upper passage 73.Downward deflection of the jet sheet through the lower passage 74similarly is accomplished by pressurizing the upper control plenum 78.The control air pressure alternately supplied to the control plenums 78and 79 is switched at a rate to produce the desired oscillationfrequency of the jet flap.

Inasmuch as an airfoil having a fluidically controlled jet flapaccording to the present invention operates to modify the flow of airacross and downstream of the airfoil, the airflow-modifying capabilitiesof such airfoils are not limited to use on an aircraft. For example,FIG. 4 shows a pair of airfoils and SI mounted to extend across thewidth of the model section of an otherwise conventional wind tunnel 52.The airfoils 50 and 51 are spaced apart from each other sufficiently topermit a test model 53 to be disposed either between or downstream ofthe two airfoils.

Each ofthe airfoils 50 and includes ajet flap 54 and 55, respectively.located in the trailing edge of the airfoil and inciuding a main plenum.an upper control plenum, and a lower control plenum, all as describedabove with reference to FIGS, 2 and 3. Pressurized air from a suitablesource 56 is supplied through a valve 57 and a conduit 58 to the mainplenums of each of the jet flaps 54 and 55. Each ofthe two upper controlplenums is connected to receive pressurized air from a conduit 66connected to a valve 63, while the two lower control plenums aresimilarly connected through a conduit 67 to a valve 64. The valves 63and 64, which receive pressurized air from a conduit 62, areinterconnected so that one of the valves is open while the other valveis closed. The valve operating mechanism 65 alternately switches the twovalves 63 and 64 between their respective flow positions so that airpressure is alternately applied to both of the upper control plenums andthen to both of the lower control plenums to cause synchronousdeflections of the jet sheets 68 and 69. It is understood, of course,that the valves 64 and the valve operating mechanism 65 are shown by wayof example only and that other suitable apparatus such as a fluidicswitching mechanism or the like can be substituted.

Operation of the FIG, 4 embodiment is depicted in FIG. 5, where the jetflaps 54 and 55 are shown producing downwardly deflected jet sheets 68and 69, resulting from pressurized air applied to both of the uppercontrol plenums and, of course, the main plenums of the jet flaps. Sinceboth of the airfoils 50 and SI are spaced from the roof and the floor,respectively, of the wind tunnel, the synchronous deflection of the jetsheets modifies the airflow along the test model 53. In the FIG. 5embodiment, for example, the placement of the test model 53 within theregion extending from between the two airfoils to at least about fourairfoil chord lengths downstream of the airfoils provides a usefulregion of suitably uniform deflected air flow. The deflection of the jetsheets can be varied and oscillated by the valve actuating mechanism 65to subject the test model to an oscillatory flow of air. The inventionembodiment depicted in FIGS. 4 and 5 thus provides a technique forvarying the direction of airflow around a model in a wind tunnel withoutresort to the cumbersome and costly movable vanes and associatedactuating mechanisms heretofore used.

While the described embodiments of the present invention all pertain toa fluidically deflected jet flap with an airfoil, it is known in the artthat hydrofoils can be equipped with jet flaps whereby the Iifi of ahydrofoil is incrementally varied by the flow of a liquid, such aswater, from a slot along the trailing edge of the hydrofoil.Accordingly, the jet flap deflection techniques and applications of thepresent invention are applicable to hydrofoils as well as airfoils;deflection of a hydrofoil jet sheet is obtainable, for example, byimpinging a control stream of liquid substantially at right angles tothe jet sheet.

Deflection of the jet sheet is accomplished in the embodiments describedherein by impinging a fluid stream onto one side of the jet sheet, withthe result that the pressure differential produced across the jet sheetcauses the jet sheet to be deflected away from the region of greaterpressure. Such deflection of the jet sheet also is obtainable, however,if the deflection-producing pressure differential is caused by applyingsuction to one side of the jet sheet to lower the fluid pressurethereat, relative to the ambient fluid pressure affecting the other sideof the sheet. This is accomplished, for example, by applying suction tothe control plenum 28 of FIG. 2 to reduce the fluid pressure on theunder side of the jet sheet 17, with the result that the jet sheet isdeflected downwardly.

It should be understood, of course, that the foregoing relates to onlypreferred embodiments of the invention and that numerous modificationsor alterations may be made therein without departing from the spirit andthe scope of the inven tion, as set forth in the appended claims.

What is claimed is:

I. A fluid dynamic apparatus comprising:

a fluid foil having a trailing edge and including a fluid flow surfaceover which fluid flows in a direction generally toward said trailingedge in the operation of said foil;

a plenum contained within said foil and connected to receive fluidpressure;

fluid passage means disposed in said foil, said fluid passage meansbeing in fluid flow communication between said plenum and a certainspanwise extent of said foil trailing edge and being operative to directa jet sheet fluid stream in a substantially chordwise, downstreamdirection from said foil trailing edge;

first control fluid flow means disposed in said foil and selectivelyconnected in fluid flow communication with a source of fluid pressure,

said first control fluid flow means positioned to direct a control fluidstream into flow direction modifying impingemerit along the spanwiseextent of said jet sheet fluid stream emitted from said fluid flow meanswhen said first control fluid flow means is in open fluid flowcommunication with said source of fluid pressure; and,

second control fluid flow means disposed in said foil and selectivelyconnected in fluid flow communication with a source of fluid pressure;

said second control fluid flow means positioned to direct a controlfluid stream into flow modifying impingement along the spanwise extentof said jet sheet fluid stream emitted from said fluid flow means whensaid second control fluid flow means is in open fluid flow communicationwith said source of fluid pressure;

said first and second control fluid flow means being disposed onopposite sides of said jet sheet fluid stream to selectively direct therespective control fluid streams in opposed relationship toward said jetsheet fluid stream.

2. Apparatus as in claim 1, wherein said control fluid streams impingesaid jet sheet fluid stream substantially perpendicularly thereto.

3. Apparatus as in claim I, wherein:

said fluid flow means comprises a plurality of passageways definingopenings in fluid communication with said plenum and arrayed in aspanwise direction along said portion of said trailing edge to directpremurized fluid flowing therethrough to form a fluid layer extendinggenerally downstream of said trailing edge;

said first control fluid flow means comprises a first control conduitselectively connected to a source of fluid pressure and disposed in aspanwise direction along said trailing edge portion, said first conduitbeing displaced to one side of said fluid layer and having a pluralityof openings positioned to direct a fluid stream for direction modifyingimpingement on said fluid layer; and

said second control fluid flow means comprises a second control conduitselectively connected to a source of fluid pressure and disposed in aspanwise direction along said trailing edge portion, said second conduitbeing displaced to the other side of said fluid layer to be positionedopposite and spaced apart from said first control conduit,

said second control conduit having a plurality of openings positioned todirect a fluid stream for direction modifying impingement on said fluidstream.

4. Apparatus as in claim 3, wherein said openings of both said first andsecond control conduits are positioned to direct the respective fluidstreams emanating therefrom for substantially perpendicular impingementonto said fluid layer.

5. Apparatus as in claim 3, wherein said foil comprises an element ofthe lift generation and modification portion of a vehicle; and furthercomprising:

control signal means producing an output signal in response to a desiredvehicle attitude adjustment;

flow control means connected to control the flow of fluid to each ofsaid first and second control conduits,

said flow control means connected to be responsive to the output signalof said control signal means and being operative to supply fluid to theappropriate one of said control conduits to deflect the direction offlow of said fluid layer in a direction to impart to said foil a forceincrement tending to accomplish the desired attitude adjustment of thevehicle.

6. Apparatus for modifying fluid flow in a fluid flow region,

comprising:

passageway means defining a fluid flow region through which the flow offluid in a certain direction is permitted;

at least one fluid foil having a trailing edge and disposed in saidpassageway means so that the span of said foil is substantiallytransverse to the direction of fluid flow therethrough;

a fluid plenum disposed in said foil and connected to a source of fluidpressure;

fluid passage means disposed in said foil and communicating fluid flowbetween said plenum and the trailing edge of said foil to establish ajet sheet fluid layer extending generally downstream of said foiltrailing edge;

first control fluid passage means disposed in said foil to direct afluid stream into flow deflecting impingement along the spanwise extentof and at a substantial angle with one side of said fluid flow whichestablishes said jet sheet fluid layer;

second control fluid passage means disposed in said foil to direct afluid stream into flow deflecting impingement along the spanwise extentof and at a substantial angle with the other side of said fluid flowwhich establishes said jet sheet fluid layer; and control meansconnected to selectively supply fluid flow to either of said first andsecond control fluid passage means.

7. Apparatus as in claim 6, further comprising:

another fluid foil having a trailing edge and disposed in saidpassageway means so that the span of said other foil is substantiallytransverse to the direction of fluid flow therethrough,

said other fluid having a fluid flow plenum, fluid passage means, firstcontrol fluid passage means, and second control fluid passa e means thesame as the corresponding elements are rsposed 111 and functionallymterrelate with said one foil,

said fluid flow plenum of said other airfoil being connected to a sourceof fluid pressure;

said foils being mounted spaced apart from each other in said fluid flowregion in a dimension substantially transverse to said certain directionof passageway means fluid flow; and

control means connected to selectively supply fluid flow to either ofsaid first and second control fluid passage means of said other foil.

8. Apparatus as in claim 7, wherein:

said control means is connected to selectively supply fluid flow to bothof said first control fluid passages or to both of said second controlfluid passages so that said control means causes synchronous flowdeflecting impingement of the control fluid streams with the respectivejet sheet fluid layers.

is a s s a

1. A fluid dynamic apparatus comprising: a fluid foil having a trailingedge and including a fluid flow surface over which fluid flows in adirection generally toward said trailing edge in the operation of saidfoil; a plenum contained within said foil and connected to receive fluidpressure; fluid passage means disposed in said foil, said fluid passagemeans being in fluid flow communication between said plenum and acertain spanwise extent of said foil trailing edge and being operativeto direct a jet sheet fluid stream in a substantially chordwise,downstream direction from said foil trailing edge; first control fluidflow means disposed in said foil and selectively connected in fluid flowcommunication with a source of fluid pressure, said first control fluidflow means positioned to direct a control fluid stream into flowdirection modifying impingement along the spanwise extent of said jetsheet fluid stream emitted from said fluid flow means when said firstcontrol fluid flow means is in open fluid flow communication with saidsource of fluid pressure; and, second control fluid flow means disposedin said foil and selectively connected in fluid flow communication witha source of fluid pressure; said second control fluid flow meanspositioned to direct a control fluid stream into flow modifyingimpingement along the spanwise extent of said jet sheet fluid streamemitted from said fluid flow means when said second control fluid flowmeans is in open fluid flow communication with said source of fluidpressure; said first and second control fluid flow means being disposedon opposite sides of said jet sheet fluid stream to selectively directthe respective control fluid streams in opposed relationship toward saidjet sheet fluid stream.
 2. Apparatus as in claim 1, wherein said controlfluid streams impinge said jet sheet fluid stream substantiallyperpendicularly thereto.
 3. Apparatus as in claim 1, wherein: said fluidflow means comprises a plurality of passageways defining openings influid communication with said plenum and arrayed in a spanwise directionalong said portion of said trailing edge to direct pressurized fluidflowing therethrough to form a fluid layer extending generallydownstream of said trailing edge; said first control fluid flow meanscomprises a first control conduit selectively connected to a source offluid pressure and disposed in a spanwise direction along said trailingedge portion, said first conduit being displaced to one side of saidfluid layer and having a plurality of openings positioned to direct afluid stream for direction modifying impingement on said fluid layer;and said second control fluid flow means comprises a second controlconduit selectively connected to a source of fluid pressure and disposedin a spanwise direction along said trailing edge portion, said secondconduit being displaced to the other side of said fluid layer to bepositioned opposite and spaced apart from said first control conduit,said second control conduit having a plurality of openings positioned todirect a fluid stream for direction modifying impingement on said fluidstream.
 4. Apparatus as in claim 3, wherein said openings of both saidfirst and second control conduits are positioned to direct therespective fluid streams emanating therefrom for substantiallyperpendicular impingement onto said fluid layer.
 5. Apparatus as inclaim 3, wherein said foil comprises an element of the lift generationand modification portion of a vehicle; and further comprising: controlsignal means producing an output signal in response to a desired vehicleattitude adjustment; flow control means connected to control the flow offluid to each of said firSt and second control conduits, said flowcontrol means connected to be responsive to the output signal of saidcontrol signal means and being operative to supply fluid to theappropriate one of said control conduits to deflect the direction offlow of said fluid layer in a direction to impart to said foil a forceincrement tending to accomplish the desired attitude adjustment of thevehicle.
 6. Apparatus for modifying fluid flow in a fluid flow region,comprising: passageway means defining a fluid flow region through whichthe flow of fluid in a certain direction is permitted; at least onefluid foil having a trailing edge and disposed in said passageway meansso that the span of said foil is substantially transverse to thedirection of fluid flow therethrough; a fluid plenum disposed in saidfoil and connected to a source of fluid pressure; fluid passage meansdisposed in said foil and communicating fluid flow between said plenumand the trailing edge of said foil to establish a jet sheet fluid layerextending generally downstream of said foil trailing edge; first controlfluid passage means disposed in said foil to direct a fluid stream intoflow deflecting impingement along the spanwise extent of and at asubstantial angle with one side of said fluid flow which establishessaid jet sheet fluid layer; second control fluid passage means disposedin said foil to direct a fluid stream into flow deflecting impingementalong the spanwise extent of and at a substantial angle with the otherside of said fluid flow which establishes said jet sheet fluid layer;and control means connected to selectively supply fluid flow to eitherof said first and second control fluid passage means.
 7. Apparatus as inclaim 6, further comprising: another fluid foil having a trailing edgeand disposed in said passageway means so that the span of said otherfoil is substantially transverse to the direction of fluid flowtherethrough, said other fluid having a fluid flow plenum, fluid passagemeans, first control fluid passage means, and second control fluidpassage means the same as the corresponding elements are disposed in andfunctionally interrelated with said one foil, said fluid flow plenum ofsaid other airfoil being connected to a source of fluid pressure; saidfoils being mounted spaced apart from each other in said fluid flowregion in a dimension substantially transverse to said certain directionof passageway means fluid flow; and control means connected toselectively supply fluid flow to either of said first and second controlfluid passage means of said other foil.
 8. Apparatus as in claim 7,wherein: said control means is connected to selectively supply fluidflow to both of said first control fluid passages or to both of saidsecond control fluid passages so that said control means causessynchronous flow deflecting impingement of the control fluid streamswith the respective jet sheet fluid layers.